[tip:perf/core] perf evlist: Reference count the cpu and thread maps at set_maps()

[tip-bot for Arnaldo Carvalho de Melo <tipbot@zytor.com>]

Commit-ID:  a55e5663761366fb883f6f25375dd68bc958b9db
Gitweb:     http://git.kernel.org/tip/a55e5663761366fb883f6f25375dd68bc958b9db
Author:     Arnaldo Carvalho de Melo <acme@redhat.com>
AuthorDate: Wed, 17 Feb 2016 10:57:19 -0300
Committer:  Arnaldo Carvalho de Melo <acme@redhat.com>
CommitDate: Thu, 18 Feb 2016 10:48:37 -0300

perf evlist: Reference count the cpu and thread maps at set_maps()

We were dropping the reference we possibly held but not obtaining one
for the new maps, which we will drop at perf_evlist__delete(), fix it.

This was caught by Steven Noonan in some of the machines which would
produce this output when caught by glibc debug mechanisms:

  $ sudo perf test 21
  21: Test object code reading                                 :***
  Error in `perf': corrupted double-linked list: 0x00000000023ffcd0 ***
  ======= Backtrace: =========
  /usr/lib/libc.so.6(+0x72055)[0x7f25be0f3055]
  /usr/lib/libc.so.6(+0x779b6)[0x7f25be0f89b6]
  /usr/lib/libc.so.6(+0x7a0ed)[0x7f25be0fb0ed]
  /usr/lib/libc.so.6(__libc_calloc+0xba)[0x7f25be0fceda]
  perf(parse_events_lex_init_extra+0x38)[0x4cfff8]
  perf(parse_events+0x55)[0x4a0615]
  perf(perf_evlist__config+0xcf)[0x4eeb2f]
  perf[0x479f82]
  perf(test__code_reading+0x1e)[0x47ad4e]
  perf(cmd_test+0x5dd)[0x46452d]
  perf[0x47f4e3]
  perf(main+0x603)[0x42c723]
  /usr/lib/libc.so.6(__libc_start_main+0xf0)[0x7f25be0a1610]
  perf(_start+0x29)[0x42c859]

Further investigation using valgrind led to the reference count imbalance fixed
in this patch.

Reported-and-Tested-by: Steven Noonan <steven@uplinklabs.net>
Report-Link: http://lkml.kernel.org/r/CAKbGBLjC2Dx5vshxyGmQkcD+VwiAQLbHoXA9i7kvRB2-2opHZQ@mail.gmail.com
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Wang Nan <wangnan0@huawei.com>
Fixes: f30a79b012e5 ("perf tools: Add reference counting for cpu_map object")
Link: http://lkml.kernel.org/n/tip-j0u1bdhr47sa511sgg76kb8h@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
 tools/perf/util/evlist.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/tools/perf/util/evlist.c b/tools/perf/util/evlist.c
index d81f13d..a7eb0ea 100644
--- a/tools/perf/util/evlist.c
+++ b/tools/perf/util/evlist.c
@@ -1181,12 +1181,12 @@ void perf_evlist__set_maps(struct perf_evlist *evlist, struct cpu_map *cpus,
 	 */
 	if (cpus != evlist->cpus) {
 		cpu_map__put(evlist->cpus);
-		evlist->cpus = cpus;
+		evlist->cpus = cpu_map__get(cpus);
 	}
 
 	if (threads != evlist->threads) {
 		thread_map__put(evlist->threads);
-		evlist->threads = threads;
+		evlist->threads = thread_map__get(threads);
 	}
 
 	perf_evlist__propagate_maps(evlist);